In routine operation of nuclear power plants, as well as research in the fields of radiation chemistry and reactor materialogy, remote viewing of objects placed in strong ionizing radiation fields furnishes valuable information to the personnel. Currently existing remote viewing systems permit not only direct observation of the processes occurring in radiation fields, but also their photography and cinematography. According to their design features, the remote viewing systems can be classified into the following three main categories: optical systems, such as viewing ports in protection cells, periscopes, and systems with a fibre-optics image translator; electron-optical systems, such as TV cameras, and electron-optical converters; and composite systems in which a periscope or a bundle of optic fibres is combined with a TV camera.
Despite the great variety of designs, the existing remote viewing systems function for extended periods only at an average ionizing radiation dose rate P.ltorsim.100 R/sec. This restriction is imposed by the limited radiation-optical stability of the optical elements used in a remote viewing system. The problem of enhancing the radiation-optical stability of optical elements is partially solved by introducing into their material stabilizing additives, for example, CeO.sub.2 added to inorganic glass. Optical elements made of glasses containing stabilizing additives may be employed up to an integral absorbed dose of about 10.sup.8 rads (at a dose rate of about 100 R/sec, the integral absorbed dose of about 10.sup.8 rads can be accumulated during six months). It should be noted that materials with CeO.sub.2 additives feature pronounced radioluminescence in a strong ionizing radiation field, the intensity of this radioluminescence increasing with that of the field. Therefore, a fibre probe for inspecting nuclear reactor cores, whose design is described by N. S. Capani in his book "Fibre Optics" (Moscow, "Mir" Publishers, 1969, p. 360), does not permit viewing of the core of an operating reactor, but is used for examining the surfaces of core components, checking the quality of assembly, and so on, only during the period prior to operation.
An example of a combined remote viewing system is the device for investigating fuel elements of a nuclear reactor, disclosed in French Patent Application No. 2,298,859 published in "Bulletin officiel de la propriete industrielle", No. 39; Cl. G 21C 17/06. This device comprises a prism endoscope with a tilted mirror, interfaced with a TV camera.
The device under consideration can be employed in the core of a nuclear reactor when the gamma and high-energy beta radiation dose rates do not exceed .about.100 R/sec.
Also known is a device for remote viewing of objects in ionizing radiation fields, whose fibre-optics channel intended for transmission of the object's image beyond the biological shield against ionizing radiation comprises an entrance lens and a bundle of individual optic fibres, one end of the bundle being in direct proximity to the entrance lens, while the other end is beyond the biological shield (cf. N. S. Capani, "Fibre Optics", "Mir" Publishers, Moscow, 1969, p. 360).
This device, just like those described above, operates only in weak ionizing radiation fields, has a short service life and is practically useless in strong ionizing radiation fields.